The production of hydrocarbon fluids such as crude oil or gas from a subterranen reservoir is normally achieved by tapping into the reservoir with one or more wells from the surface. When the subterranean natural pressure is insufficient to force the hydrocarbon fluids to the surface, production can be stimulated or improved by the introduction of a thermal stimulant such as steam or hot water.
The primary effect of the latter, when introduced to a reservoir containing crude oil or the like, by way of an injection well, is to decrease the density of the heavy fluids. This change affords them greater mobility through the substrate. The less dense fluids can therefore be forced to the surface with minimal reservoir pressure.
This method of thermal stimulation particularly by steam or hot water injection, has long been utilized by the petroleum industry. It does, however, add an expense factor to the overall production costs, particularly in the instance of heavier crude oils.
A further factor bearing consideration occurs in the instance of older substerranean reservoirs or hydrocarbon containing fields. Over a period of time, thermal stimulation might become a necessary expedient if a production rate is to be sustained. It is therefore a general practice that to stimulate production, steam, regardless of its quality, is forced into the hydrocarbon containing reservoir thereby to increase or sustain a desired production rate.
Usually, the source of the steam for such a purpose is generated at a central location and piped to the well or to a plurality of wells at which it is to be used. The quality of the steam can be controlled at its source. However, since it is injected at a point of use remote from the steam generator, the quality will be decreased. This decrease in quality will to some degree be dependent on the distance, the efficiency of the steam conductor insulating medium, and phase splitting at pipe tests.
In the instance of large and diverse hydrocarbon containing fields, often numerous wells and well patterns are employed. In this situation, it has been found desirable and economical to regulate both the flow rate, and the quality of the steam which is utilized for any particular well or group of wells.
More specifically, in the instance of older wells, the quality and the flow rate of the injection steam need not be as high as the quality and flow rate of steam which is injected into newer wells. Thus, to epitomize the effective utilization of steam which is generated at a relatively high quality, it is necessary to reduce its quality and flow rate preferably at the point of use rather than at the point where it is generated.
In effect, high quality steam can be used most effectively and with minimal waste, by being introduced into a well that does not require such a degree of thermal stimulation. Rather, the well requires only a lower grade of steam to achieve a desired production rate.
Among the simpler methods for reducing the quality of any steam flow is to intermix water with the steam, thereby automatically reducing its quality. It is known, however, that the intermixing multiphase flow in this manner, where the temperature differentials of the two mediums are diverse, the reaction can be violent on the mixer or mixing equipment.
More specifically, it is known that at low steam flow rates the mixer will be subjected to severe vibration and shaking as a result of the intermixing of the steam with the water at a much lower temperature. This phenomenon is generally attributed to the violent condensation shock as the steam contacts cold water.
Unless the mixing equipment is made structurally adequate to overcome the violent reaction between the water and steam, damage could result especially where thermal stimulation through reduced quality steam is continuous over a period of time.
It is therefore an object of the invention to provide a system and the equipment therefor which is adapted to provide the necessary stimulating medium either in the form of low, or controlled quality steam or hot water, for injection into a hydrocarbon containing substrate.
A further object is to provide a simple steam-water mixer that will furnish an outflow of lowered quality steam and hot water without undue vibratory motion or shaking as a result of the mixing process.